Rare genetic diseases provide scientifically useful models that help to elucidate mechanisms underlying common disorders. In fact, improving understanding of rare diseases has historically led to major advances in medical science. Our studies with the rare red blood disorder, congenital dyserythropoietic anemia type I (CDA-1), have similar potential outcomes. CDA-1 is an autosomal recessive disorder of ineffective erythropoiesis marked by anemia and the presence of multinucleated erythroblasts with internuclear chromatin bridges in the bone marrow. Ultrastructural erythroid features include spongy heterochromatin and invagination of the nuclear membrane, carrying cytoplasmic content into the nucleus. Codanin, the protein defective in CDA-1, is a chromatin-binding protein but its function remains unknown. Preliminary data show that codanin is differentially expressed during erythropoiesis and megakaryopoiesis, and that it binds to important erythroid and megakaryocytic genetic loci. Interestingly, erythroid and megakaryocytic lineages arise from a common precursor, the megakaryocytic-erythroid progenitor. Furthermore, diminished expression of codanin in CDA-1 results in erythroid multinuclearity, which is a hallmark of megakaryopoiesis. Thus, we hypothesize that codanin is involved in the regulation of erythroid and megakaryocytic lineages. The goal of this project is to define how codanin, the protein defective in CDA-1, regulates erythroid and megakaryocytic genes by its binding to key regulatory DNA regions. We will identify how codanin gene perturbation affects erythroid and megakaryocytic differentiation by employing codanin knockdown and overexpression (wild type and mutant codanin) systems. Hematopoietic assays specific for erythroid and megakaryocytic lineages will be conducted to identify the hematopoietic phenotype induced by codanin gene perturbation. CDA-1-specific gene expression profiles will be identified by RNA-seq studies. Furthermore, we will understand how codanin regulates EKLF expression by conducting luciferase reporter assays, and identify codanin-interacting proteins by immunoprecipitation and mass spectrometry assays. We have conducted these studies in K562 cells and have begun experiments in human CD34+ cells. We will also extend our studies to the megakaryocyte erythroid progenitors. This project will help us elucidate the role that codanin plays in control o erythropoiesis and megakaryopoiesis in attempts to better understand the mechanisms of bone marrow failure disorders.